Ed, I think this is the case for the boat I am buying; it looks painted with a high-quality paint too.  I will take a picture of it when I go back for the survey.  Mine is definitely steel and the rusting (superficial, at least at this point) is along a weld line - the rest of it 90% looks really good.  It could be associated with the bolting like yours, so I will take a closer look.  I may go ahead and have one fabricated out of aluminum like yours, it is a good idea.  Not sure if the fabricator needs it in hand to copy or is there a drawing/specs out there?  I would like to have one on the shelf for when I do pull the mast, but for now I will clean this one up and epoxy paint it as my first project when I get the boat home! Thanks for the fabricator as I have added them to my references!